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An electronic warning system for grape downy mildew— based on models for the infection of leaves of Vitis lambrusca, production of sporangia by Plasmopara viticola in lesions, and sporangial survival—was tested over 7 years in Ohio. Grapevines were sprayed with metalaxyl plus mancozeb (Ridomil MZ58) when the warning system indicated that environmental conditions were favorable for sporulation and subsequent infection. Over the 7 years, plots were sprayed from one to four times according to the warning system, and from four to 10 times according to the standard calendar-based schedule (depending on the date of the initiation of the experiment). The warning system resulted in yearly reductions of one to six sprays (with median of three sprays). Disease incidence (i.e., proportion of leaves with symptoms) in unsprayed plots at the end of the season ranged from 0 to 86%, with a median of 68%. Incidence generally was very similar for the warning-system and standard-schedule treatments (median of 7% of the leaves with symptoms), and both of these incidence values were significantly lower (P < 0.05) than that found for the unsprayed control, based on a generalized-linear-model analysis. Simplifications of the disease warning system, where sprays were applied based only on the infection or sporulation components of the system, were also effective in controlling the disease, although more fungicide applications sometimes were applied. Effective control of downy mildew, therefore, can be achieved with the use of the warning system with fewer sprays than a with a standard schedule.

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Hydrophobic and/or hydrophilic kaolin particle film treatments to peach (Prunus persica (L) Batsch) trees were evaluated for crop and pest management capabilities in six studies from 1997 to 2000. Unsprayed control and standard treatments, the latter consisting of a commercial pesticide program, were included for comparison. Treatments in initial studies were applied via handgun, which resulted in a uniform and heavy deposit of kaolin after the first application. In contrast, treatments in subsequent studies used airblast equipment, which provided a uniform but less dense coverage, even after multiple applications. Results showed that both formulations of kaolin provided control of oriental fruit moth (Grapholita molesta (Busck)), plum curculio (Conotrachelus nenuphar (Herbst)) and Japanese beetle (Popillia japonica Newman) that was comparable with or better than the standard pesticide program. Effective management of late season catfacing insects (tarnished plant bugs Lygus lineolaris (Palisot de Beauvois) and stinkbugs Acrosternum hilare (Say), Euschistus servus (Say), and E tristigmus (Say)) and leafrollers (undetermined species) was also observed, although kaolin applications significantly increased phytophagous mite (Panonychus ulmi (Koch)) levels. In contrast to arthropod management, kaolin failed to control either peach scab (Cladosporium carpophilum (Von Thumen)) or rusty spot (Podosphaera leucotricha (Ell and Ev) ES Salmon) in any of the 4 years of the study. However, hydrophobic kaolin provided effective brown rot (Monilinia fructicola (G Winter) Honey) control when applied via handgun, and partial control when applied via airblast; hydrophilic kaolin failed to provide any control. These results suggest that hydrophobicity and deposit density may be important factors for effective disease management. The application of kaolin significantly delayed fruit maturation, increased fruit size and increased soluble solids relative to the standard. This effect, attributed to a reduction in plant stress, also resulted in increased fruit number and yield on young trees, indicating that an accentuated beneficial response from kaolin applications may be possible.

Organometallic copper, consisting of a mixture of copper abietate, copper linoleate, and copper oleate (CuALO), is important for postbloom management of bacterial spot in New Jersey peach and nectarine orchards. Rotation of CuALO with oxytetracycline reduces cost and helps prevent (or delay) resistant organisms. However, because copper is also phytotoxic, higher rates and inorganic coppers have not been utilized. A study was conducted on ‘Encore’ peach and ‘Redgold’ nectarine to determine the quantitative relationship between copper concentration (metallic equivalent) and phytotoxicity. Different rates of CuALO and copper hydroxide (CuOH) were applied seven times postbloom. Foliar injury and defoliation increased with number of applications and copper concentration. Maximum ‘Encore’ defoliation was 10 to 17%, while ‘Redgold’ sustained 30 to 35% leaf loss. CuOH caused similar or less leaf injury and defoliation than CuALO. No injury was observed on fruit, even at three times the labeled metallic copper rate of CuALO. Fruit size and soluble solids were not influenced by copper. Estimates of foliar density and tree volume indicated that sufficient photosynthetic capacity existed to allow acceptable leaf damage and loss from copper applications. These results showed that inorganic coppers may be viable alternatives to organometallic copper for postbloom bacterial spot control; nectarine may be more sensitive to copper injury than peach; and higher rates of metallic copper, above the current commercial rate, can be applied to peach. In the latter case, greater amounts of copper may provide longer residual activity and improved bacterial spot control on highly susceptible cultivars.